|Abstract||Objectives: The aim of the present study was to examine the role of cannabis in road crashes in South Australia, with a particular focus on the extent to which crashes involving cannabis also involve alcohol.
Methods: Hospital data, police-reported crash data, and the results of forensic tests of blood samples for drugs and alcohol were collected for 1490 crash participants admitted to hospital. A sample of 135 Coronerís reports were also examined to determine the role of alcohol and cannabis in fatal crashes.
Results: The three years of linked data for hospital admission cases revealed that alcohol played a greater role in road crashes than other drugs. Approximately one in five drivers or riders had a BAC above the legal limit of 0.05. Routine testing for cannabis, methamphetamine and MDMA revealed a drug positive rate of approximately one in ten of those tested, with over half of these positive to cannabis. More than a third of cannabis cases also involved alcohol. The majority of those who were positive to alcohol had a BAC above 0.15 g/100ml. BACs were similarly high among drivers positive to both alcohol and cannabis.
The findings of the hospital data and the Coroners reports were consistent with each other in terms of providing confirmation that alcohol is still the drug associated with the greatest level of road trauma on South Australian roads. Furthermore, alcohol was also present in around half of the cannabis cases, and, when present, tended to be present at very high levels. The results of this study emphasise that, although drug driving is clearly a problem, the most important form of impaired driving that needs to be the target of enforcement is drink driving. Roadside drug testing is important but should not be conducted in such a way that reduces the deterrent value of random breath testing.